Electric timepiece regulator



April 1969 TOSHI TERAYAMA 3,441,753

ELECTRIC TIMEPIECE REGULATOR Filed July 19, 1967 Sheet of 2 TUNING FORKf 3 i l I f5 /6 r TRANSISTOR FREQUENCY ELECTRO- TIME AMPLIFIER DIVIDERMECHANICAL INDCATOR FLlP-FLOPS CONVERTER 4 SELF OSCILLATOR m II II I, pI 0 II 2 P 1 1 F D 0 Am I F R RI wwmwww A TTORNEY- April 1969 TOSHITERAYAMA 3,441,753

ELECTRIC TIMEPIECE REGULATOR Sheet 3 of 2 Filed July 19, 1967 5 ilmg/wAazaw ATTORNEY United States Patent US. Cl. BIO-8.2 Claims ABSTRACT OFTHE DISCLOSURE There is disclosed a regulator for an electric timepiecewhereby the oscillation frequency of the frequency standard isselectively varied from the outside of the timepiece case by a variableresistor. Three piezoelectric electrode elements are secured to a tuningfork frequency standard. A transistor amplifier has its input connectedto one of the electrodes and with its output fed back to a second of theelectrodes. The variable resistor is connected between ground and thethird electrode, whereby the oscillation frequency of the tuning fork isselectively varied in accordance with the resistance of the variableresistor.

Background of the invention The present invention generally relates toan electric timepiece regulator and more particularly to anelectromechanical frequency standard regulator.

Presently, in order to adjust a mechanical timepiece oscillator such asa tuning fork or tuning bar, it was necessary to mechanically adjust theoscillator, such as by grinding away a portion of the oscillators top orbase portion. Such methods of mechanical adjustment is unsatisfactorybecause of the change in the oscillator resonant frequency caused byaging.

Another presently used method for oscillator frequency adjustmentrequired the adjustment of the center of gravity of the mechanicaloscillator by shifting of oscillator mass distribution. Such anadjustment method was found to be undesirable since it requiredrendering the mechanical oscillator stationary in order to carry out thefrequency adjustment process. This was found to be a serious drawbackparticularly in the case of highly accurate timepieces, since itprecluded continuous frequency adjustment as well as frequencyadjustment from the case interior.

Furthermore, the method of frequency adjustment by adjusting thenegative electromagnetic stiffness of the oscillator by means of amagnet is disadvantageous since this adjustment has been found to atfectmuch the resonant frequency temperature coefiicient of the oscillator.

It is therefore an object of the present invention to provide anelectric timepiece regulator which is relatively uncomplicated inconstruction whereby frequency adjustment may be accomplished fromoutside the timepiece case.

It is a further object of the present invention to provide an electrictimepiece regulator which is operative to provide continuous frequencyadjustment while the mechanical oscillator is in motion.

Another object of the present invention is to provide an electrictimepiece regulator which is operative to provide continuous frequencyadjustment without affecting the other timepiece parameters, such as,frequency-temperature coefficient, frequency-battery voltage, and powerconsumption characteristics.

Brief description of the invention In accordance with the principles ofthe present invention there is provided a timepiece regulator comprisingmechanical oscillator means and a plurality of piezoelectric elementssecured to the mechanical oscillator means. Electrical amplifier meanshas its input connected to one of the piezoelectric elements and itsoutput connected to a second of the piezoelectric elements. There isfurther provided a varita'ble resistor which is connected to a third ofthe piezoelectric elements which is operative to selectively vary theoscillation frequency of the mechanical oscillator means in accordancewith the resistance value of the variable resistor.

Brief description of the drawings For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a partial schematic diagram and partial functional blockdiagram depicting a preferred embodiment of the present invention.

FIG. 2 is a perspective view of a mechanical oscillator and regulatorconstructed in accordance with the principles of the present invention.

FIG. 3 is a perspective view of another mechanical oscillator andregulator constructed in accordance with the principles of the presentinvention.

FIG. 4 is a perspective view of yet another mechanical oscillator andregulator constructed in accordance with the principles of the presentinvention.

FIG. 5 is a schematic diagram depicting the electroacoustical equivalentcircuit of preferred embodiments of FIGS. 24.

FIG. 6 is a schematic diagram of a simplified version of the equivalentcircuit of FIG. 5.

FIG. 7 is a graphical representation depicting the variation ofequivalent capacitance C and equivalent resistance R as a function ofthe variation of resistance R.

FIG. 8 is a graphical depiction of the variation in resonant frequencyAW W0 Description of embodiments Referring to FIG. 1 there is shownpartial schematic and partial functional block diagram of a self-excitedoscillator 1 constructed in accordance with the principles of thepresent invention. Oscillator 1 comprises a tuning fork oscillator 2whose output at piezoelectric element P is fed to transistor amplifier 3whose output is fed back to tuning fork 2 via piezoelectric element D toprovide an amount of electrical energy sufiicient to keep tuning fork 2oscillating. A selectively variable resistor R is connnected betweenpiezoelectric element F secured to the other leg of tuning fork 2 andground, and is operative to selectively vary the frequency of the tuningfork output. The output of amplifier 3, which is an amplified electricalsignal same as applied on piezoelectric element D is applied tofrequency divider 5, which may suitably comprise a chain of flip-flopcircuits.

The output of frequency divider 5 is applied to electromechanicalconverter 6, which may suitably comprise a pulsed motor, whose output isapplied to time indicator 7 which may suitably comprise a gear trainsystem in conjunction with suitable display means.

Referring to FIG. 2, there is shown a tuning fork 2 of a material havinga substantially constant coeflicient or elasticity, such as Elinvar orNi-Span C which is secured to its base plate by means of set screwsthrough its support (not shown). Adhesively secured to the tuning forkbottom portion 2a are piezoelectric electrode elements P, D and F whichare connected to their output terminals p, d and 1 respectively by leadwires as shown. Electrode elements P, D and F are made of piezoelectricmaterial such as barium titanate or lead zirconatetitanate. Electrode Pis operative to detect the mechanical motion of tuning fork 2 and toproduce an electrical signal proportional thereto, while electrode D isoperative to convert the electrical feedback signal from transistoramplifier 3 to mechanical driving motion which is applied to tuning fork2.

Resistor R, which is connected between electrode F and ground terminalg, is selectively variable to thereby vary the equivalent capacity inthe series resonant circuit representing the motional impedance, i.e.,acoustical impedance of the mechanical oscillator to thereby selectivelyvary the resonant frequency of the mechanical oscillator of the presentinvention.

Referring to FIG. 3, there is depicted another embodiment of amechanical oscillator constructed in accordance with the presentinvention whereby the piezoelectric electrode elements P and F areadhesively secured to one prong 2c of tuning fork 2, while the remainingpiezoelectric electrode element D is secured to the opposite tuning forkleg 2b.

Referring to FIG. 4, there is shown yet another embodiment of amechanical oscillator constructed in accordance with the principles ofthe present invention, whereby a tuning bar 2A is supported by wires Wand W at its theoretical node points while having its ends free.Piezoelectric electrode elements P, D and F are adhesively secured totuning bar 2A at its upper surface, and as in the embodiments of FIGS. 2and 3 have leads extending therefrom to their respective terminals p, dand 1.

Referring to FIG. 5, there is shown an acoustic schematic diagram of theequivalent circuit of the mechanical oscillator of the presentinvention. It is noted that when terminals X-X are short-circuited, thecircuit of FIG. 5 represents the equivalent circuit of a mechanicaloscillator having no F electrode. A A and A are force factorsrepresenting the electro-mechanical conversion efficiency of thepiezoelectric elements while C 1, C and C represent the electrostaticcapacities thereof. The coefficient m, s, and r corresponding to theequivalent mass, stiffness (reciprocal of compliance or equivalentcapacity) and the equivalent mechanical resistance of the oscillatorrespectively while terminal pairs p-p", d-d' and f-f' represent thepiezoelectric element terminals respectively.

It is understood that the force factors A A and A and C01, C02: C03, arenot necessarily equal to each other. However, to facilitate analysis ofthe circuit of FIG. 5 let A1=Az A3 A, and let C =C =C =C Then theequivalent circuit of FIG. 5 reduces to the circuit of FIG. 6. In FIG.6, X-X' corresponds to terminals fand L=m/A C=A /s and R=r /A From theabove it follows that where W is the angular frequency of the inputsignals.

When the oscillator is in self-oscillation in conjunction with amplifier3, the oscillation frequency will be very close to the mechanicalresonant frequency W i.e., W W

Referring to FIG. 6, when terminals p-p are short circuited, withterminals d-d being driven by a constant voltage source, the resonantfrequency W may be expressed as and 1 oo V35 Referring to Equations 1, 2and 3 above, it is seen that the resonant frequency W will have amaximum value of when C =C with R'=oo, and W will have a minimum value Wwhen Cx: 00 with R: O.

In order for the mechanical oscillator to have a high Q factor, sincec/c is generally quite small, i.e., 0/0 is in the range of 10- to 1O themaximum regulation range may be expressed as AW Wo tinuously varied fromW... to (1+ while the resistance of resistor R which is connected acrossterminals fis varied from 0 to 00 with the maximum slope of the changein frequency occurring when 1 I R W 0 with no variations in the othertimepiece parameters being experienced.

In one experiment, utilizing a tuning fork arrangement as shown in FIG.2 the following results were achieved:

with the maximum regulation range being while the resistance of resistorR was varied from 0 to 2 megohms.

In another experiment using a similar sized tuning fork 2 but utilizinga larger F electrode, a maximum regulation range of was achieved.

It is understood that the tuning fork of FIG. 3 may be utilized 'whereit is desired to obtain a larger regulation range. In such a case, sincethe force factor will be larger, c/c will be greater by providing alarger piezoelectric element at the point where the higher stressoccurs, e.g., on the tuning fork leg near the yoke portion. Theseprinciples may also be applied to the tuning bar 2A shown in FIG. 4,where maximum regulation may be obtained by having piezoelectricelectrode F secured to bar 2A at the center portion thereof, where thehighest stress will occur during oscillation.

Referring to FIG. 1, it is understood that frequency divider 5 may beeliminated if electromechanical converter 6 is frequency matched withoscillator 1, and if necessary, a power amplifier may be providedbetween the output of oscillator '1 and the input to converter 6, if thepower output of oscillator 1 is insufiicient.

It is further understood that the mechanical oscillator of the presentinvention is not necessarily limited to a piezoelectric driven systembut may suitably incorporate an electromagnetic driven system.

In view of the above it is seen that the following advantages overconventional timepiece regulators are obtained with the timepieceregulator of the present invention, as follows. An electric timepiecemay be easily and continuously regulated from outside the case over arange of :5 seconds or more a day merely by selectively varyingregulating resistor R from outside of the timepiece case. There iscompletely avoided the heretofore common problems caused by regulationsuch as frequency shift due to aging, loss of balance of the tuning forkprongs, stopping of tuning fork oscillation, variation of thefrequency-temperature characteristics as well as the frequency-batteryterminal voltage characteristics. Furthermore, the maximum regulationrange may be chosen by selecting the size of the piezoelectric elementand by selectively locating the element on the mechanical oscillator.

While there have been shown particular embodiments of the presentinvention, it is understood that it is not wished to be limited therto,since modifications can be made thereto without departing from thespirit and scope of the present invention, and it is intended to coversuch modifications in the claims appended hereto.

What is claimed is:

1. A timepiece regulator comprising, mechanical oscillator means, aplurality of piezoelectric electrode elements secured to said mechanicaloscillator means, electrical amplifier means having its input connectedto one of said piezoelectric electrode elements and its output connectedto a second of said piezoelectric electrode elements, and a variableresistor connected to a third of said piezoelectric electrode elements,and the base of said mechanical oscillator means, said resistor beingoperative to selectively vary the oscillation frequency of saidmechanical oscillator means at said one piezoelectric electrode elementin accordance with the resistance value of said resistor.

2. A timepiece regulator as defined in claim 1 wherein said mechanicaloscillator means is a tuning fork.

3. A timepiece regulator as defined in claim 1 wherein said mechanicaloscillator means is a tuning bar.

4. A timepiece regulator as defined in claim 2 wherein saidpiezoelectric electrode elements are secured to the yoke of said tuningfork.

5. A timepiece regulator as defined in claim 2 wherein saidpiezoelectric electrode elements are secured to the prongs of saidtuning fork.

6. A timepiece regulator as defined in claim 3 wherein saidpiezoelectric electrode elements are secured to one surface of saidtuning bar.

7. A timepiece regulator as defined in claim 1 wherein saidpiezoelectric elements are three in number.

8. A timepiece regulator as defined in claim 7 wherein the output ofsaid electrical amplifier means is connected to an electromechanicalconverter for driving time indicator means connected thereto.

9. A timepiece regulator as defined in claim 8 including frequencydividing means having its input connected to the output of saidelectrical ampli-fier means and its output connected to the input ofsaid electromechanical converter. f

10. A timepiece regulator as defined in claim -8 including a poweramplifier having its input connected between said electrical amplifiermeans and said electromechanical converter for driving saidelectromechanical converter.

References Cited UNITED STATES PATENTS 1,781,513 11/1930 Holweck 84-4091,849,271 3/ 1932 Bower 58-23 2,747,090 5/1956 Cavalieki 331-1563,024,429 3/1962 Cavalieki 331-156 3,243,951 4/ 1966 Kawakami 331-1163,325,743 6/1967 Blum 310-83 3,336,529 8/1967 Tygart 310-82 3,343,3659/1967 Vosseler 310-81 J. D. MILLER, Primary Examiner.

US. Cl. X.R.

